Orofacial (mastication and chewing) dysfunction is one of the hallmarks of orofacial pain. A device that measures such dysfunction in an animal model of pain would be of great utility in scientific testing of ideas concerning the mechanical and molecular mechanisms involved in pain and in evaluating drug efficacy for the treatment of orofacial pain. An objective animal assay that quantifies pain-induced dysfunction like that seen clinically in patients is not available. Most previous animal studies of orofacial pain evaluate a painful acute cutaneous stimulus e.g., heat in the head or neck of the animal rather than evaluating pain in animal models of conditions such as oral cancer, TMJ disorders, or muscle inflammation in the head and neck. One of the principle reasons that orofacial pathologies e.g., cancer or TMJ disorders are often not employed to elicit pain in these animal studies is that investigators have no objective assay or device to evaluate and quantify the forms of orofacial dysfunction that pain produces in these conditions. Previous animal studies have evaluated stereotyped behaviors (e.g., rubbing and flinching of the head) for use as indices of acute orofacial pain. Pain assays of stereotyped behaviors are not high throughput and not objective. In addition, they have not proven useful for objectively measuring chronic orofacial pain in animals. To infer pain in a model of chronic temporomandibular joint (TMJ) disorders or masticatory muscle pain, studies quantifying meal duration, meal size and inter-meal interval have been developed. These meal (feeding) studies are limited in their ability to resolve behavioral changes due to orofacial pain versus pain originating elsewhere in the body because rodents with nontrigeminal pain also demonstrate a reduced feeding rate. To show a significant difference between orofacial and nontrigeminal pain, investigators have looked at inter-meal interval. However, inter-meal interval is an even more indirect method of demonstrating oral dysfunction resulting from pain. All meal studies used to evaluate orofacial pain are fundamentally prone to error because they are potentially confounded by variables that affect appetite. Appetite can be altered by analgesics, systemic disease, time of day, duration of the study and reward associated with consumption. Moreover, pain that originates outside of the trigeminal system reduces appetite and affects feeding in humans and rodents. The limitations of meal (feeding) assays can be avoided by directly measuring gnawing function not associated with consumption. There is currently no automated device available that quantifies gnawing function to evaluate orofacial pain. A gnawing assay for mice was developed by Ayada et al. (Am J Physiol Regul Integr Comp Physiol 2000; 279(6):R2042-2047) whereby the mass of the material gnawed away from a plastic strip was used as a proxy for gnawing activity. Our assay measures an entirely different outcome variable (time to complete a discrete gnawing task) and our device to carry out our assay does so in an automated fashion unlike the Ayada assay. No current or known automated device evaluates the character, duration or restriction of oral function in animals such that dysfunction secondary to a painful orofacial pathology in the animal is directly comparable to pain induced dysfunction in patients.